Pets might have the ability to stimulate their caregivers, in particular the elderly, giving people someone to take care of, someone to exercise with, and someone to help them heal from a physically or psychologically troubled past. Animal company can also help people to preserve acceptable levels of happiness despite the presence of mood symptoms like anxiety or depression. Having a pet may also help people achieve health goals, such as lowered blood pressure, or mental goals, such as decreased stress. There is evidence that having a pet can help a person lead a longer, healthier life. In a 1986 study of 92 people hospitalized for coronary ailments, within a year, 11 of the 29 patients without pets had died, compared to only 3 of the 52 patients who had pets. Having pet(s) was shown to significantly reduce triglycerides, and thus heart disease risk, in the elderly. A study by the National Institute of Health found that people who owned dogs were less likely to die as a result of a heart attack than those who did not own one. There is some evidence that pets may have a therapeutic effect in dementia cases. Other studies have shown that for the elderly, good health may be a requirement for having a pet, and not a result. Dogs trained to be guide dogs can help people with vision impairment. Dogs trained in the field of Animal-Assisted Therapy (AAT) can also benefit people with other disabilities.